Modern regulatory standards in all US jurisdictions require specific provisions for plugging oil and natural gas wells before they are abandoned. A well is plugged typically by setting mechanical or cement plugs in the wellbore at specific intervals to prevent fluid flow. The plugging process usually requires a workover rig and cement pumped into the wellbore and water-based slurries of cement are typically the basic materials used to plug most wells.
The plugging and abandoning (P&A) of oil and gas wells that are no longer economically viable for production, or which have wellbore issues that require closure, remains a typical, but costly, practice in the oil and gas production business. Production wells that are no longer economical to operate must be plugged to prevent the oil and gas reservoir fluids or saltwater from migrating uphole over time and possibly contaminating other formations and or fresh water aquifers.
However, P&A continues to be even more important, not only to meet Federal and State environmental regulations but also because of new recovery techniques. As older oil and gas fields are re-entered to exploit bypassed reserves or to develop reserves deemed uneconomical in the past, the plugged and abandoned wells within the fields become a potential problem as new technologies are applied. These new recovery techniques can increase the reservoir pressure due to the injection of fluids for oil recovery. When this higher pressure is applied to unplugged or poorly plugged wells, there is a chance that the formation fluids will bypass the plugging materials and migrate uphole. This can cause problems with the fresh water aquifers in the area by allowing gas, oil or salt water to contaminate the fresh water.